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author | Jianchao Wang <jianchao.w.wang@oracle.com> | 2018-08-21 15:15:04 +0800 |
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committer | Jens Axboe <axboe@kernel.dk> | 2018-08-21 09:02:56 -0600 |
commit | f5bbbbe4d63577026f908a809f22f5fd5a90ea1f (patch) | |
tree | a6d8a1e7329b4160285b79a0565a45b53a2809f6 /drivers/block/DAC960.c | |
parent | d48ece209f82c9ce07be942441b53d3fa3664936 (diff) |
blk-mq: sync the update nr_hw_queues with blk_mq_queue_tag_busy_iter
For blk-mq, part_in_flight/rw will invoke blk_mq_in_flight/rw to
account the inflight requests. It will access the queue_hw_ctx and
nr_hw_queues w/o any protection. When updating nr_hw_queues and
blk_mq_in_flight/rw occur concurrently, panic comes up.
Before update nr_hw_queues, the q will be frozen. So we could use
q_usage_counter to avoid the race. percpu_ref_is_zero is used here
so that we will not miss any in-flight request. The access to
nr_hw_queues and queue_hw_ctx in blk_mq_queue_tag_busy_iter are
under rcu critical section, __blk_mq_update_nr_hw_queues could use
synchronize_rcu to ensure the zeroed q_usage_counter to be globally
visible.
Signed-off-by: Jianchao Wang <jianchao.w.wang@oracle.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'drivers/block/DAC960.c')
0 files changed, 0 insertions, 0 deletions